nova-dhcpbridge: hostname = argv[4] causes IndexError

Using nova trunk (bzr 1370).

I'm getting the following error from nova-dhcpbridge.log:

(nova): TRACE: Traceback (most recent call last):
(nova): TRACE: File "/usr/bin/nova-dhcpbridge", line 127, in <module>
(nova): TRACE: main()
(nova): TRACE: File "/usr/bin/nova-dhcpbridge", line 118, in main
(nova): TRACE: hostname = argv[4]
(nova): TRACE: IndexError: list index out of range
(nova): TRACE:

According the the dnsmasq man page (for the dhcp-script option):

       -6 --dhcp-script=<path>
              Whenever a new DHCP lease is created, or an old one destroyed,
              the executable specified by this option is run. <path> must be
              an absolute pathname, no PATH search occurs. The arguments to
              the process are "add", "old" or "del", the MAC address of the
              host, the IP address, and the hostname, if known.

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Looks like the 4th arg for hostname is not getting passed to our nova-dhcpbridge script.